POS0110 ARTHROSCOPY IS NECESSARY TO DETECT CARTILAGE DAMAGE IN NON-ADVANCED KNEE OA
Authors: M. Mateos-Fernández, F. Lopez-Oliva, C. Herencia, J. Fernández-Jara, I. Masa, E. Calvo, J. Espinosa, E. Naredo, R. Largo, G. Herrero-Beaumont
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Knee osteoarthritis (OA) is characterized by the slow deterioration of articular cartilage that takes years to destroy the tissue. Magnetic resonance imaging (MRI) is commonly used for quantitative assessment of articular cartilage, and thus proposed by many authors as a substitute for X-ray, which requires longer periods of time --at least 3 years between images-- to detect changes. Drug agencies continue to consider X-ray outcomes preferable for clinical trials, as the superiority of MRI over X-ray is not clear. More importantly, these measurements have not been compared with direct visualization of the cartilage. <h3>Objectives</h3> To evaluate cartilage width as well as early cartilage lesions by X-ray and MRI techniques, comparing these observations with those obtained by direct visualization of cartilage during arthroscopy (ARTH) in a population with non-advanced knee OA. <h3>Methods</h3> We prospectively recruited 105 patients (&gt;18 y.o) with knee pain of more than 3 months´ duration who underwent diagnostic knee ARTH due to uncertain origin knee pain or meniscal tear. WOMAC score was used to assess joint pain and function. Standardized weight-bearing extended anteroposterior digital X-ray were performed aligning the center of the beam with de femorotibial joint space. Images without correct alignment of the tibial plateau were discarded. By X-ray, OA grade was assessed by the Kellgren and Lawrence score (KLS). Medial and lateral joint space width (JSW) was measured on X-ray at the mid-surface of the affected knees in a blind manner. By MRI, cartilage lesions were classified into 3 categories (MRI score, MRI-S): normal (no damage), low grade (fibrillation or thickening &lt;50%) or high grade (thickening &gt;50% or loss). Knee ARTH was performed through two portals according to standard practice and cartilage lesions assessed by Outerbridge score (OBS). Bonferroni-corrected ANOVA test for continuous variables, Chi-square or Fisher's test for discrete variables, normality with Shapiro-Wilk and Kolmogorv-Smirnov tests, concordance between groups with weighted Kappa index, correlation between OBS and cartilage measurement with Spearman's correlation were performed employing Python 3.7 and SPSS25 for Windows 10. <h3>Results</h3> The correlation between X-ray JSW measurement and the OBS was null (r=-0.052). No good agreement was found between the OA grade assessed by KLS and OBS, nor between MRI-S and OBS. Cartilage deterioration evaluated by X-ray and MRI showed a lower degree of tissue damage than that observed by ARTH visualization (Table 1). <h3>Conclusion</h3> ARTH enabled to detect cartilage damage with higher precision than X-ray or MRI. In addition, the ARTH assessment was able to explain the different pain and function levels, since patients with different OBS showed different WOMAC scores. MRI can detect joint lesions in the extra-articular space or related to bone damage, which are not observable with ARTH. Therefore, for clinical trials assessing structure progression, ARTH evaluation combined with MRI would be the most appropriate techniques to accurately measure cartilage deterioration. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.